1. Field of the Invention
The present invention relates to a method for forming trench isolation, and particularly, to a method for forming shallow trench isolation without microscratches by using High-Density-Plasma (HDP) process.
2. Description of the Prior Art
Chemical-Mechanical polishing (CMP) is conventionally used in semiconductor manufacturing to achieve global planarity. The chemical-mechanical polishing generally includes a rotating table for holding a wafer, where slurry and a polishing pad are applied. Chemical-Mechanical polishing is usually used to planarize trenches, such as shallow trench isolation. During trench refilling step in forming a shallow trench isolation, as shown in Figure 1A, silicon dioxide 110 is deposited over a semiconductor substrate 112, thereby refilling the trench 114. Figure 1B shows the cross section of the formed shallow trench isolation 110A, which is formed by planarizing the vapour deposited silicon dioxide 110 by a conventional Chemical-Mechanical polishing until the top surface of the silicon nitride layer 116 atop of the substrate 112 is exposed.
Unfortunately, due to the inherent drawbacks of the chemical-mechanical polishing mechanism, the surface of the shallow trench isolation 110A can not be made substantially planar, and thus possesses microscratch problem which seriously yields degradation in the manufactured device.
For the foregoing reasons, there is a need for a method of forming shallow trench isolation without aforementioned microscratches problem.